Three channel cache-coherency socket protocol

Abstract

A system and method are disclosed for communicating coherency information between initiator and target agents on semiconductor chips. Sufficient information communication to support full coherency is performed through a socket interface using only three channels. Transaction requests are issued on one channel with responses given on a second. Intervention requests are issued on the same channel as transaction responses. Intervention responses are given on a third channel. Such an approach drastically reduces the complexity of cache coherent socket interfaces compared to conventional approaches. The net effect is faster logic, smaller silicon area, improved architecture performance, and a reduced probability of bugs by the designers of coherent initiators and targets.

What is claimed is:  
     
       1. A system, comprising:
 an initiator; 
 a target; and 
 a socket configured to enable communication of information between the initiator and the target, the socket consisting of:
 a first channel; 
 a second channel; and 
 a third channel, wherein the socket is configured to allow communication of information relating to cache-coherency, and wherein:
 the initiator is configured to send command requests through the first channel and to receive command responses through the second channel, and 
 the target is configured to send intervention requests through the second channel and to receive intervention responses through the third channel. 
 
 
 
     
     
       2. The system of  claim 1  further comprising a second socket through which the target is configured to act as an initiator. 
     
     
       3. The system of  claim 1  further comprising a second socket through which the initiator is configured to act as a target. 
     
     
       4. The system of  claim 1  further comprising a second socket, arranged such that an agent is configured as both an initiator on one socket and a target on the other. 
     
     
       5. The system of  claim 1 , wherein the information is packetized. 
     
     
       6. The system of  claim 1 , wherein the initiator is further configured to ensure forward progress of the second channel independently of forward progress of the first channel. 
     
     
       7. The system of  claim 1 , wherein the target is further configured to ensure forward progress of the third channel independently of forward progress of the first and second channels. 
     
     
       8. The system of  claim 1 , wherein the information refers to lines of addressable space. 
     
     
       9. The system of  claim 1 , wherein the socket is further configured to allow communication of information related to address translation service. 
     
     
       10. The system of  claim 1  wherein at least one piece of information on the second channel is configured to transfer command response information and intervention request information. 
     
     
       11. The system of  claim 1  wherein the initiator is further configured to receive the command responses in an order that is different from an order in which the command requests were sent to the target. 
     
     
       12. The system of  claim 1  wherein the target is further configured to send the command responses in an order that is different from an order in which the command requests were sent from the initiator. 
     
     
       13. The system of  claim 1  wherein the command responses may be received in any order. 
     
     
       14. The system of  claim 1  wherein the intervention responses are received in an order that is different from an order in which the intervention requests were sent. 
     
     
       15. The system of  claim 1  wherein the intervention responses may be received in any order. 
     
     
       16. A method of communicating information relating to cache-coherency, the method comprising:
 transferring intervention request information on a first channel from a target to an initiator; 
 transferring intervention response information on a second channel from the initiator to the target; 
 transferring command request information on a third channel from the initiator to the target; and 
 transferring command response information on the first channel. 
 
     
     
       17. The method of  claim 16  wherein the initiator accepts information on the first channel without waiting to send information on the third channel. 
     
     
       18. The method of  claim 16  wherein the initiator sends information on the second channel without waiting to send information on the third channel or receive information on the first channel. 
     
     
       19. The method of  claim 16  wherein the target sends information on the first channel without waiting to receive information on the third channel. 
     
     
       20. The method of  claim 16  wherein the target accepts information on the second channel without waiting to receive information on the third channel or send information on the first channel. 
     
     
       21. The method of  claim 16  in which the information is packetized. 
     
     
       22. The method of  claim 21  wherein the packetized information comprises at least one packet that transfers command response information and intervention request information. 
     
     
       23. A system comprising:
 an initiator; 
 a target; and 
 a socket configured to enable communication of information between the initiator and the target, the socket comprising:
 a first channel; 
 a second channel; and 
 a third channel,
 wherein the initiator is configured to send command requests through the first channel and to receive command responses through the second channel; and 
 the target is configured to send intervention requests through the second channel and to receive intervention responses through the third channel. 
 
 
 
     
     
       24. The system of  claim 23  further comprising a second socket through which the target is configured to act as an initiator. 
     
     
       25. The system of  claim 23  further comprising a second socket through which the initiator is configured to act as a target. 
     
     
       26. The system of  claim 23  further comprising a second socket, arranged such that an agent is configured as both an initiator on one socket and a target on the other. 
     
     
       27. The system of  claim 23 , wherein the information is packetized. 
     
     
       28. The system of  claim 23 , wherein the initiator is further configured to ensure forward progress of the second channel independently of forward progress of the first channel. 
     
     
       29. The system of  claim 23 , wherein the target is further configured to ensure forward progress of the third channel independently of forward progress of the first and second channels. 
     
     
       30. The system of  claim 23 , wherein the information refers to lines of addressable space. 
     
     
       31. The system of  claim 23 , wherein the socket is further configured to allow communication of information related to address translation service. 
     
     
       32. The system of  claim 23  wherein at least one piece of information on the second channel is configured to transfer command response information and intervention request information. 
     
     
       33. The system of  claim 23  wherein the command responses are received in an order that is different from an order in which the command requests were sent. 
     
     
       34. The system of  claim 23 , wherein the command responses are received in any order. 
     
     
       35. The system of  claim 23 , wherein the intervention responses are received in an order that is different from an order in which the intervention requests were sent. 
     
     
       36. The system of  claim 23  wherein the intervention responses may be received in any order.